Generally, in this type of apparatus, an air vent is formed in an external wall of a casing, and atmospheric air sucked from the outside is used to cool the inside of the apparatus, and then, is discharged. It is known that blast paths inside the apparatus efficiently cool the periphery of alight source lamp, the periphery of a power supply board and the like becoming high temperatures, and the periphery of a photoelectric converter susceptible to heat.
For example, Patent Document 1 proposes a mechanism for arranging an air vent and blast fan in a part of a casing and supplying cooling air to inside the casing. In the Document, the direction of a blast path is disposed in a main scanning direction of a carriage for reciprocating. Further, Patent Document 2 also proposes a similar blast path structure.
It is also proposed in Patent Document 3, Patent Document 4 and the like that an air filter is disposed in the blast path in the cooling mechanism for thus sucking atmospheric air from the outside.